Margaret was the eldest daughter of Béla III of Hungary and his first wife Agnes of Antioch. She was a younger sister of Emeric of Hungary. Her younger siblings were Andrew II of Hungary and Constance of Hungary. Two other siblings, Solomon and Stephen, are mentioned in the "Europäische Stammtafeln: Stammtafeln zur Geschichte der Europäischen Staaten" (1878) by Detlev Schwennicke. They reportedly died young.
Her husband died in February, 1204. Later that year the widowed Margaret married Boniface of Montferrat, who was soon to become king of Thessalonica. To Boniface she bore a son Demetrius in 1207. In the same year, on his father's death, Demetrius became king of Thessalonica. }} |}